The present invention relates to a data segment synchronization ("sync") detection circuit and a method thereof, and more particularly, to a circuit for detecting a data segment synchronization signal by using a correlation characteristic of transferred sync pulses which are respectively inserted at the beginning of data segment lines, and a method thereof.
For years, efforts have been made to develop a large screen, high resolution television. As a result of these efforts, high definition television (HDTV) broadcasts, based on multiple sub-Nyquist sampling encoding (MUSE) in an analog transmission mode, are available in Japan.
In the United States, the Grand Alliance (GA) committee has proposed technical standards for a HDTV system. The GA committee has adopted the vestigial side band (VSB) modulation as a GA-HDTV modulation standard. Specifically, the adopted modulation standards include an 8-VSB using eight levels and a 16-VSB using mode and a high speed cable mode, respectively, as modulation standards in the GA-HDTV.
Meanwhile, to insure proper synchronization between television transmitter and receiver, a sync signal (pulse) is inserted into the signal transmitted from a television station, at the beginning of each horizontal line. The receiver detects these sync pulses in the received broadcast signal, and processes the required signal. It should be noted that each of the 8-VSB and 16-VSB modes require a specific transmission data format for each horizontal line, which is called a data segment.
FIG. 1 shows the structure of one data segment for 8-VSB modulation of a GA-HDTV transmission. The data segment is constituted of 832 symbols comprised of 828 symbols of data and a 4-symbol sync pulse. The data segment sync pulse is inserted into an 8-level ("-7" through "+7") digital data stream, at the starting portion of each data segment. The sync pulse includes a predetermined pattern of four symbols having the sequential levels of +5, -5, -5 and +5, and the data (i.e., information signal) is formed of randomized signal levels.
In the receiver which receives the GA-HDTV signals, a data segment sync pulse is detected in the initial 4-symbol period of each data segment. Signals are then processed according to the detected data segment sync pulse. However, when a carrier frequency offset or symbol frequency offset is present in an input signal, the number of symbols in one data segment can be altered, and the position of the sync pulse can change accordingly. When this occurs, the sync detection circuit cannot properly detect the synchronization signal.